Method of manufacture of rectangular tubes



M y 1, 1929. E. CHALLET 1,713,742

' METHOD OF MANUFACTURE OF RECTANGULAR TUBES Filed July 14, 1927 INVENTOR.

a. Chums BY W A TTORNEYS.

Patented- May 21, 1929. I

UNITED STATES PATENT OFFICE. v

ETIENNE CHALLET, OF GENEVA, SWITZERLAND, ASSIGNOR T MAURICE ARTHUR BORED, OF PONTARLIER, FRANCE.

METHOD OF MANUFACTURE OF RECTANGULAR TUBES.

Application filed July 14, 1927,'Serial No.

Tubes of rectangular section have already been manufactured by drawing, startmg for example with a tube of circular cross section. It is very easy to obtain in this way"v tubes in which the wall has everywhere the same thickness, that is to say in which the angles are rounded; it is, on the other hand, much more diflicult to obtain a tube with sharp angles, that is tot-say having at the corners amuch greater thickness than over the remainder of the eriphery; in order to obtain this result the ibllowing procedure is usually adopted; a tube .with rounded angles is drawn which is thicker than the sharp angled tube to be obtained and, for ex ample by grinding or milling, it'is reduced to the desired thickness at the same time as the angles are formed. This mode of operation presents the disadvantage that there is a complete thinning operation to be performed by grinding or milling; in addition this reduction in thickness removes the outer metal layer, which layer is of great use because the cold working has increased its strength. The tube blank may also be passed immediately through an exactly rectangular draw plate, but this blank must then be a little larger than the finished tube in order to provide-the necessary material 3 to fill up the angles. Now this is diflicult to effect because as the amount of material in question is very small it is difiicult to judge it exactly; usually too much will be allowed, the efilect of which is to make the sides of the tube slightly concave. If a mandrel is placed insidethe tube in order to prevent this deformation the surplus material will be pressed into the angles of the drawplate in excess and will cause these angles to be torn ofi. The object of the'invention is to provide a method of making rectangular metal tubes I having plane surfaces and sharp angles. The method according to this invention conished rectangular pipe. Fig. 2 is a plan sists in passing a tube blankthrough a draw.

205,795, and in Switzerland June 11, 1927.

view of a draw plate used in the method for making rectangular pipes according to this invention. Figs. 3 and 4 are fragmentary endv1ews of a pipe at different stages during the manufacturing process.

4 1s a drawplate the drawing orifice in which is of rectangular cross section and is formed-by a rectangle 5 extended at each angle in small escapementchambers 6. The tube blank which has to pass through the drawplate is somewhat larger than the tube 3 produced from the latter, the surplus material being free to expand into the chambers'6 filling them to. a varying extent according to the thickness of the blank. It will thus be posisble to obtain correct tubes even if this thickness varies somewhat. The

burrs 7 (see Fig. 3) produced upon the tube issuing from the drawplate by the chambers 6 are easily removed, for example by grinding or milling. The tube with its burrs could also be first passed through a rolling mill which would make the burrs occupy the position shown in Fig. 4, and these burrs be removed afterwards, for example by grinding.

The tubes manufactured in thisway have sharp angles, so that they are adapted for use as rules for exam le, or for the rods of sliding calipers, etc., fbr which uses the rectangular'tubes with rounded corners would not be suitable.

I claim: j

1. The method of making rectangular metal tubes with plane surfaces and sharp angles, which consists in passing a tube blank through a draw plate having an orifice of substantially rectangular cross section metal tubes having plane surfaces and sharp angles, which consists in passing a tube blank through a draw plate having an orifice of. substantially rectangular cross section, the corners of the rectangle extending into small chambers for the escapement of surplus material, thereby reventing the surplus material from pro ucing a deformation of the tube'walls, and then removing this surplus material. V

3. The method of making rectangular metal tubes having plane surfaces and sharp rial from producing a deformation of the angles, which consists in passing a tube blank tube walls, passing the drawn tube through through a-draw plate having an orifice of a rolling mill to press down the burrs pro- 1 substantially rectangular cross section, the duced by the escapement chambers, and then 5 corners of the rectangle extending into small removing the burrs by mechanical means.

chambers for the escapement of surplus ma- In testimony whereof I aflix my signature. terial, thereby preventing the surplus mate- ETIENNE CHALLET. 

